Hydraulic actuators

ABSTRACT

In an hydraulic actuator comprising a cylinder and piston assembly of which one element is part of a rigid stationary member contact of hydraulic fluid with the said member is prevented by a thin metal shell, and a sliding seal is provided between the shell and the other element.

United States Patent 1191 Harrison Oct. 16, 1973 HYDRAULIC ACTUATORS [56] References Cited [751' Inventor: kiniibny'wiillmiiariisdn, UNITED STATES PATENTS Birmingham, England 2,386,477 10/1945 Kraft 188/366 73] Assignee: cirimgnimiia iaiimmgilam,' 2,695,080 11/1954 De Bee England 3,160,238 12/1964 Jagenberg 188/366 [22] Filed: July 1971 Primary Examiner-George E. A. Halvosa 21 App], 5 9 9 Attorney-Scrivener, Parker Scrivener & Clarke [30] Foreign Application Priority Data [57] ABSTRACT July 4, 1970 Great Britain 32,529/70 In an hydraulic actuator comprising a Cylinder and P ton assembly of which one element is part of a rigid 52 US. Cl 188/72.4, 92/171, 188/366, stationary member eenteet of hydraulic fluid with the 192/70 2 192/ 5 AA said member is prevented by a thin metal shell, and a 51 1111. C1. Fl6d 65/32 Sliding Seal is Provided between the Shell and the ether [58] Field of Search 188/715, 72.4, 72.5, element- 702 7 Claims, 6 Drawing Figures PATENTEDUCT 16 1975 SHEEIEUF 4 HYDRAULIC ACTUATORS This invention relates to improvements in hydraulic actuators, primarily to improvements in piston and cylinder actuators. 7

When either the piston or cylinder or an hydraulic actuator is part of a much larger component such as a gear case the lack of hydraulic soundness in the larger component sometimes causes trouble. Also, the expense of machining the sealing surfaces in such a large component can become significant. The object of the invention is to overcome the hydraulic soundness problem without having to resort to an expensive separately machined part.

According to our invention an hydraulic actuator comprises at least two co-operating memebers capable of relative movement in response to hydraulic pressure, the co-operating surface of one member being covered or lined with a thin metal shell which prevents contact of the hydraulic fluid with that member and a sliding seal being provided between the other member and the shell.

Preferably the thin shell is cold formed by pressing or drawing.

In a piston and cylinder actuator the thin shell may be a pressing closely fitted to either the piston or to the cylinder so that it is structurally supported against hydraulic pressure. In a convenient arrangement the shell is fitted to the inner surface of the cylinder.

Since the shell is cold formed its finish is particularly suitable for an hydraulic sliding sea] as compared with a machined or ground finish. Also, this finish is comparatively inexpensive compared with machining or grinding.

The ports for supplying fluid to the actuator may enter via passages in the piston or they may be formed by pipes integral with or fixed to the shell or by openings in the shell locally sealed to the cylinder.

In an actuator for an annular piston disc brake the shell may be extended from the cylinder to provide projecting abutment surfaces for the static discs and to provide a flange or other means to secure the shell against rotation in the cylinder. The abutments and flange may be easily sheared and bent from a pressed shell.

Two embodiments of our invention as applied to annular piston disc brakes are illustrated by way of example in the accompanying drawings in which:

FIG; 1 is a vertical section of a brake assembly in a plane containing the axis of the brake;

FIG. 2 is a similar section of a brake incorporating some modifications;

FIG. 3 is a fragmentary section on the line 3-3 of FIG. 1;

FIG. 4 is a fragmentary radial section of a brake having a single rotatable disc;

FIG. 5 is a fragmentary section of a brake in which the piston is stationary and carries a sheet metal cover working in a movable cylinder;

FIG. 6 is a similar section of a modification.

The brake illustrated in FIGS. 1 and 2 is located within the transmission casing l of a tractor or like vehicle. Two brake discs 3, 4 are keyed on a ring 5 which is itself keyed on a rotatable shaft 6 which is a part of the transmission gearing in the housing. Each disc carries on each face adjacent to its periphery a lining 7 of friction material which may be in the form of a continuous ring or separate arcuate pads. A static disc 8 in the form of an annulus having flat parallel faces is located between the rotatable discs and is held against rotation in the manner described below. The outer face of the disc 3 is adapted to engage a radial surface 9 on a cover 10 secured to the casing 1 by bolts 11.

An annular cylindrical recess 12 is machined in the casing 1 on the radial inner side of a step 13 and is lined by a sheet metal shell 14 which is a press fit in the recess. The shell forms an annular cylinder in which works an annular piston 15 adapted to engage the rotatable disc 4 and apply axially directed pressure to the assembly formed by the two rotatable discs and the static disc 8. The piston is provided at its rear end with a channel section or other seal 16.

The radially outer free edge or wall 17 of the shell is joggled outwardly to lie against the inner surface of the periphery of the casing. Abutments 18 are sheared out of this wall and engage in notches 19 in the periphery of the static disc 8 as shown in FIG. 3 to hold the disc against rotation, and similar abutments alternating with the abutments l8 co-operate with teeth 19' on the piston to hold that against circumferential movement in the cylinder. The inner free edge or wall of the shell is cranked radially inwards to form a flange 20 which is secured at angularly spaced points to bosses 21 on the casing by bolts 22 to hold the shell against any circumferential movement relative to the casing. Each bolt has a coned face 23 co-operating with a coned recess in the boss into which the flange 20 is forced when the bolt is tightened so that the shell is effectively held.

Fluid under pressure for actuating the piston 15 is brought into the cylinder at one or more points by a sleeve 24 passing through the casing and having a friction-welded or other fluid-tight engagement with the base or end wall of the shell. The outer end of the V sleeve has a socket 25 to receive a pipe from a master cylinder or other source of fluid under pressure.

In the modified construction shown in FIG. 2 the pressed metal shell 30 forming an annular cylinder fits within a cylindrical surface 31 of a transmission casing 32 and abuts against a radial end face of a stationary gear ring 33 fixed in the casing. The radially outer edge or wall 34 of the shell is extended and joggled outwardly to lie closely against the surface 31, which is stepped, and then is cranked outwardly to provide a radial flange 35 which is clamped between an end face of the casing 32 and a cover 36. The cover is secured to the casing by angularly spaced bolts 37 all or some of which pass through holes pierced in the flange 35 as shown in the lower part of the drawing to hold the shell against any circumferential movement relative to the casing.

Fluid under pressure is fed to the cylinder at one or more points through a sleeve 38 passing through aligned holes in the casing and the gear-ring. The inner end of the sleeve is friction weldedto the base of the cylinder over an opening. The outer end has a coned seating in a bush 39 which is screwed into a recess in the casing against a seal 40, the outer end of the bush having an internally threaded socket 41 for the connection of a pipe-line from a source of fluid under pressure.

The remainder of the assembly is the same as in the embodiment illustrated in FIG. 1 and the same reference numerals have been applied to corresponding parts.

In the brakes described above there are two rotatable discs with a single static disc between them but it will be appreciated that there may be three or more rotatable discs with two or more intermediate static discs.

FIG. 4 shows an arrangement in which there is a single rotating disc 45 carrying a friction lining 46 on each face. The disc is frictionally gripped between the radial face of a stationary ring 47 and an annular piston 48. The piston works in an annular cylinder 49 formed by part of a sheet metal pressing which is a press fit in an annular recess 50 machined in a part ofa transmission casing 51. The piston is fitted with a seal 52 on its rear face. The piston takes one half of the torque when the brake is applied and is held against circumferential movement in the cylinder by abutments sheared out of a forward extension of the outer wall of the cylinder pressing and co-operating with teeth 53 on the outer end of the piston. The torque taken by the piston is transmitted through the cylinder to the casing 51. When the cylinder is pressurised the pressure urges the cylinder into engagement with the recess in the casing and as the area of the cylinder under pressure is greater than that of the piston the friction between the cylinder and the recess is greater than that between the piston and the disc so that there is no tendency for the cylinder to move circumferentially.

FIG. shows an annular cylinder and piston assembly in which the piston 55 is the stationary member and is formed by an annular projection from a radial surface of a transmission casing 56.

A thin sheet metal pressing 57 is a press fit over the piston and provides the surface over which works a cylinder 58 formed by an annular recess in a member 59 between which and a stationary ring 60 a rotatable disc 61 is frictionally gripped when the cylinder is pressurised. Hydraulic fluid under pressure is fed to the cylinder through an axial passage 62 in the piston. A seal between the piston and cylinder is formed by O-rings 63 located in grooves in the radially inner and outer walls of the cylinder.

FIG. 6 shows another arrangement in which an annular member 65 of L cross-section co-operates with a stepped annular projection 66 on a transmission casing 67. A joggled thin sheet metal pressing 68 fits closely over the stepped face of the projection, and the member 65 is in sliding engagement with it on parts of two diameters, seals 69 and 70 being located in grooves in the parts of the member in sliding engagement with the pressing. The member 65 is held against circumferential movement relative to the pressing by teeth 71 on the member co-operating with abutments sheared out of the pressing.

Whetherthe member 65 can be regarded as the piston or cylinder part of the assembly depends on whether it is on the radially inner or outer side of the projection 66.

I claim:

1. A disc brake comprising a stationary housing of substantial mass, a radial braking surface in the housing, a rotatable shaft within the housing, at least two rotatable friction discs mounted on the shaft, a static disc located between adjacent rotatable friction discs, and

fluid pressure means for urging the disc assemblyagainst said radial braking surface, wherein said fluid pressure means comprises co-operating annular cylinder and piston elements, one of which is movable to apply axial pressure to the discs, and a thin metal shell of channel section fixed to the housing and forming a surface which, together with said movable element, constitutes said fluid pressure means, said movable element and said static disc being keyed to the shell against circumferential movement relative thereto whereby torque taken by said movable element and said static disc is transmitted through the shell to the housing.

2. A disc brake adapted to be fitted within a rigid casing and incorporating at least one stationary friction surface and one rotatable disc, axial pressure against said disc being provided by a hydrauilc actuator comprising a pair of co-operating annular cylinder and piston members, one of said members being movable by hydraulic pressure against said rotatable disc to take braking torque upon application of said brake and the second of said members being fixed to the casing, the co-operating surface between said one and second members being formed by a thin metal shell, a sliding seal being providedbetween the second member and the shell, means fixing said one member and said shell against relative circumferential movement so that the braking torque taken by said one member is transmitted directly to said shell, and means fixing said shell and said second member against relative circumferential movement so that said braking torque is transmitted by said shell directly to said second member and said casing.

3. A disc brake as in claim 2 wherein the member having its co-operating surface formed by a metal shell comprises an annular piston fixed to the casing, the outer member comprising an annular cylinder.

4. A disc brake comprising a stationary housing of substantial mass, a radial braking surface in the housing, a rotatable shaft within the housing, a rotatable friction disc mounted on the shaft, and fluid-pressure means for applying axial pressure to the friction disc to force it into engagement with said radial braking surface, wherein said'fluid pressure means comprises cooperating annular cylinder and piston elements, and a sliding seal between said elements, one of said elements being movable to apply said axial pressure to said friction disc and to take torque upon application of said brake, and the other of said elements comprising a thin metal shell of channel section fixed to the housing, and

means keying said movable element directly to the shell so as to prevent circumferential movement of said movable element relative to said shell so that the torque taken by said element on application of the brake is transmitted directly through the shell to the housing.

5. A disc brake as in claim 4 wherein the annular piston is defined by an annular projection on the housing and the thin metal shell fits closely over the projection, themovable element comprising an annular cylinder axially movable over the shell, said sliding seal being disposed between said cylinder and said shell.

6. A disc brake as in claim 4 wherein the annular movable element engages directly with the rotatable friction disc.

7. A disc brake as in claim 6 where the movable element is an annular piston. 

1. A disc brake comprising a stationary housing of substantial mass, a radial braking surface in the housing, a rotatable shaft within the housing, at least two rotatable friction discs mounted on the shaft, a static disc located between adjacent rotatable friction discs, and fluid pressure means for urging the disc assembly against said radial braking surface, wherein said fluid pressure means comprises co-operating annular cylinder and piston elements, one of which is movable to apply axial pressure to the discs, and a thin metal shell of channel section fixed to the housing and forming a surface which, together with said movable element, constitutes said fluid pressure means, said movable element and said static disc being keyed to the shell against circumferential movement relative thereto whereby torque taken by said movable element and said static disc is transmitted through the shell to the housing.
 2. A disc brake adapted to be fitted within a rigid casing and incorporating at least one stationary friction surface and one rotatable disc, axial pressure against said disc being provided by a hydrauilc actuator comprising a pair of co-operating annular cylinder and piston members, one of said members being movable by hydraulic pressure against said rotatable disc to take braking torque upon application of said brake and the second of said members being fixed to the casing, the co-operating surface between said one and second members being formed by a thin metal shell, a sliding seal being provided between the second member and the shell, means fixing said one member and said shell against relative circumferential movement so that the braking torque taken by said one member is transmitted directly to said shell, and means fixing said shell and said second member against relative circumferential movement so that said braking torque is transmitted by said shell directly to said second member and said casing.
 3. A disc brake as in claim 2 wherein the member having its co-operating surface formed by a metal shell comprises an annular piston fixed to the casing, the outer member comprising an annular cylinder.
 4. A disc brake comprising a stationary housing of substantial mass, a radial braking surface in the housing, a rotatable shaft within the housing, a rotatable friction disc mounted on the shaft, and fluid-pressure means for applying axial pressure to the friction disc to force it into engagement with said radial braking surface, wherein said fluid pressure means comprises co-operating annular cylinder and piston elements, and a sliding seal between said elements, one of said elements being movable to apply said axial pressure to said friction disc and to take torque upon application of said brake, and the other of said elements comprising a thin metal shell of channel section fixed to the housing, and means keying said movable element directly to the shell so as to prevent circumferential movement of said movable element relative to said shell so that the torque taken by said element on application of the brake is transmitted directly through the shell to the housing.
 5. A disc brake as in claim 4 wherein the annular piston is defined by an annular projection on the housing and the thin metal shell fits closely over the projection, the movable element comprising an annular cylinder axially movable over the shell, said sliding seal being disposed between said cylinder and said shell.
 6. A disc brake as in claim 4 wherein the annular movable element engages directly with the rotatable friction disc.
 7. A disc brake as in claim 6 where the movable element is an annular piston. 